U.S. Pat. No. 5,751,257 issued May 12, 1998, and U.S. Pat. No. 6,253,190 issued Jun. 26, 2001, both to Sutherland show a system including a programmable shelf tag having a bistable liquid crystal display for displaying price data and a Universal Product Code (UPC) bar code, wherein the information programmed in the display remains on the display in the absence of power. The shelf tag has a set of synchronizing indicators and corresponding electrical contacts on the frontside of the display.
The shelf tag is programmable with a hand-held device that is connected to a central computer that contains inventory and price information. The hand-held device can be used to scan the synchronizing indicators to identify the location of the electrical contacts and supplies the electrical contacts with electrical signals to write appropriate information on the shelf tag. For inventory control and price updates, the hand-held device is used to first read the UPC bar code on the shelf tag. If a price needs to be updated, the hand-held device is then used to write the appropriate price information into the tag. The hand-held device is placed into contact with the shelf tag and is moved across the tag to sequentially make contact with each of the contacts on the front side of the display. A timing track is included on the front side of the display. The hand-held device reads the timing track optically and synchronizes the signal supplied to the respective contacts as the hand-held device is moved across the display. The display includes an alignment groove and the hand-held device includes a probe that is located in the alignment groove to position the contacts of the hand-held device relative to the contacts of the display.
One problem with the system as described by Sutherland is that including the UPC as a writable element on the shelf tag, significantly increases the complexity and cost of the shelf tag. The resolution needed to produce UPC information requires 113 modules of data, and therefore requires at least a corresponding number of contacts on the front of the display.
Another problem is that the hand-held device must be translated in a preferred direction (e.g. right to left) and within a preferred translation rate to properly program the display. Yet another problem is that translating the hand-held device across the contacts tends to wear out the contacts of the hand-held device and the shelf tag over time, necessitating replacement or repair of the contacts. A further problem with the method and apparatus disclosed by Sutherland is that the electronics of the hand-held device are complicated by the need to sequentially address the contacts of the display.
There is a need therefore for an improved writable display tag and hand-held programming device that avoids the problems noted above.